Not only can you track the usual (fat, protien carbs, fiber etc), but you can check your full nutrients on "reports". I found out that I am low on calcium and vitamin d, but great on others. That has really helped me tweak my diet.

Because of uneven regulations so many supplement don't contain what they claim to contain.

And then there is the added problem that some supplements are contaminated.

There have been elite athletes who were using protein supplements only to test positive for steroids, because the batch they used was contaminated. Independent testing proved these claims were true.